Mechanical design
Week 10's assignment
Specific material and softwares used during this assignment
- Machines and electronics :
- Laser cutter for the structure
- CNC mill for the FabNet
- 3D printer for the tap system
- One Arduino board and One raspberry Pi to control the "l axis"
- Material :
- 5mm cardboard and 5mm plywood
- PLA
- Software :
- Rhino for the design of the machine and the 3D parts
- Cura for the 3D printed parts
- Atom for programming
- Arduino IDE for arduino sketches
- Other equipment :
- Silicon tubes
- Plastic taps (for acquarium aeration systems)
- Plastic connectors (for acquarium aeration systems)
For the second week of the group project, my task was still to document our work, which can be found
here.
I also worked on the fabrication of the FabNet board. Since none of the milling machines (small one not ready, big one booked all day), we made a THD board so it took quite some time. I soldered all the components, made the alimentation cable that works with a rack of 8 batteries of 1.5V. Here it is :
Then we checked the connection from FabNet to Gestalt and it was OK. :
After this we connected the Fabnet to Gestalt Node and then to USB and power and the boards were overheating, so something must be wrong on the boards. Now the CNC was available we decided to mill a FabNet board. For this we used Bas' version that can be found
here.
Here is the new version of the board, milled and soldered !
Next step was to see if we were able to communicate with the Gestalt from a computer and try to operate it. After a few unsuccessful tries we realised the FTDI cable was plugged the wrong way on the Gestalt, so we changed it and then it worked !!
Here is a screenshot of the successful program ran into the Terminal :
Then I did some other tests to determine the total distance we had for the movements of the head. The easier way to do it was to mark down the coordinates used in gestalt on a piece of tape like this :
We know that when we change the coordinates of 10 points, it actually represents 1.3cm. This will be important to know for the rest.
For the Liquid Distribution system, I also participated to the research on the mechanical part : the aim was to find the best way to deliver the liquid and we finally came up with the idea of using a tiny tap bought at a pet shop and initialy made for air distribution in fish tanks.
This is the kit that we bought :
And those are the tap and the connector for the tubes :
So the idea is to connect directly a servo-motor to the taps to open and close them. For a tap to be open, we must apply a 900° rotation to the screw. So in order to do that we would have to modify the servo-motor to suppress its rotation limit. We found this
tutorial on instructables to do this and I wanted to try :
We can see on the pictures above the process of disassembling the servo and of addind two 2.2k resistors linked together in place of the potentiometer. But the hardest part was actually to take the PCB out of the plastic case that contains it. During this process, I broke an internal part of the case itself, as well as the edge of the plastic ring around the potentiometer. As a result, even though the re soldering process worked, it was impossible to reassemble the servo-motor correctly because the potentiometer could not stand still in the plastic case. So the whole operation was a failure :(
We had no more servo to destroy at the lab, so we decided we would continue with a stepper motor instead.
See the
Group Page for the next steps of the programming and human/machine interface.